syzbot


divide error in comedi_inc_scan_progress (2)

Status: upstream: reported on 2025/11/05 08:13
Reported-by: syzbot+bb6180f965618f0f7b31@syzkaller.appspotmail.com
First crash: 1d15h, last: 1d15h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 divide error in comedi_inc_scan_progress 2 2 105d 107d 0/2 auto-obsoleted due to no activity on 2025/11/01 16:46
upstream divide error in comedi_inc_scan_progress comedi 2 45 1d11h 121d 0/29 upstream: reported on 2025/07/08 17:52

Sample crash report:
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 14374 Comm: syz.0.2448 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:comedi_inc_scan_progress+0x1a2/0x430 drivers/comedi/drivers.c:562
Code: b6 0c 19 84 c9 0f 85 b8 01 00 00 03 45 34 4c 8d a5 88 00 00 00 4c 89 e1 48 c1 e9 03 0f b6 0c 19 84 c9 0f 85 c7 01 00 00 31 d2 <41> f7 34 24 41 89 17 45 89 ec eb 0f e8 0d a7 8a f9 48 bb 00 00 00
RSP: 0018:ffffc90000007a00 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88805dba6200 R08: ffff88805dba6200 R09: 00000000000000ff
R10: dffffc0000000000 R11: fffff52001831201 R12: ffff88805dba6288
R13: 0000000000000002 R14: 0000000000000000 R15: ffff88805dba6234
FS:  00007fa18785e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a5b37ef950 CR3: 0000000036183000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 comedi_buf_write_samples+0x372/0x5d0 drivers/comedi/comedi_buf.c:646
 das16m1_handler+0x213/0x4b0 drivers/comedi/drivers/das16m1.c:413
 das16m1_interrupt+0xab/0x180 drivers/comedi/drivers/das16m1.c:470
 __handle_irq_event_percpu+0x276/0x930 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
 handle_edge_irq+0x247/0xb30 kernel/irq/chip.c:831
 generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
 handle_irq arch/x86/kernel/irq.c:240 [inline]
 __common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
 common_interrupt+0x5d/0xd0 arch/x86/kernel/irq.c:249
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
RIP: 0010:variable_ffs arch/x86/include/asm/bitops.h:319 [inline]
RIP: 0010:handle_softirqs+0x1b0/0x820 kernel/softirq.c:566
Code: 89 64 24 2c 0f b7 db 48 c7 c7 a0 b5 a9 8a e8 d7 4c 1d 09 65 66 c7 05 bd 20 b2 7e 00 00 e8 78 5b 3a 00 fb 49 c7 c6 c0 a0 a0 8c <89> 5c 24 34 b8 ff ff ff ff 0f bc 44 24 34 41 89 c5 41 ff c5 0f 84
RSP: 0018:ffffc90000007e40 EFLAGS: 00000286
RAX: 4ac8035db1dac500 RBX: 0000000000000202 RCX: 4ac8035db1dac500
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6b00
RBP: ffffc90000007f50 R08: ffffffff90da8557 R09: 1ffffffff21b50aa
R10: dffffc0000000000 R11: fffffbfff21b50ab R12: 000000000000000a
R13: 0000000000000000 R14: ffffffff8ca0a0c0 R15: ffff88802444da00
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xc7/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa9/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 ea 7c 13 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> f2 f8 e2 f6 65 8b 05 e3 41 8b 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90004917a40 EFLAGS: 00000206
RAX: 4ac8035db1dac500 RBX: 0000000000000a06 RCX: 4ac8035db1dac500
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: 0000000000000001
RBP: ffffc90004917ad0 R08: ffffffff90da8557 R09: 1ffffffff21b50aa
R10: dffffc0000000000 R11: fffffbfff21b50ab R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff971d8d40 R15: 1ffff92000922f48
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 autoconfig drivers/tty/serial/8250/8250_port.c:1307 [inline]
 serial8250_config_port+0x2697/0x39c0 drivers/tty/serial/8250/8250_port.c:3221
 univ8250_config_port+0x3b5/0x960 drivers/tty/serial/8250/8250_core.c:445
 uart_do_autoconfig drivers/tty/serial/serial_core.c:1204 [inline]
 uart_ioctl+0xddf/0xfb0 drivers/tty/serial/serial_core.c:1603
 tty_ioctl+0x926/0xdd0 drivers/tty/tty_io.c:2779
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa18698f6c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa18785e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa186be5fa0 RCX: 00007fa18698f6c9
RDX: 0000000000000000 RSI: 0000000000005453 RDI: 0000000000000003
RBP: 00007fa186a11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa186be6038 R14: 00007fa186be5fa0 R15: 00007ffdc86c3978
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:comedi_inc_scan_progress+0x1a2/0x430 drivers/comedi/drivers.c:562
Code: b6 0c 19 84 c9 0f 85 b8 01 00 00 03 45 34 4c 8d a5 88 00 00 00 4c 89 e1 48 c1 e9 03 0f b6 0c 19 84 c9 0f 85 c7 01 00 00 31 d2 <41> f7 34 24 41 89 17 45 89 ec eb 0f e8 0d a7 8a f9 48 bb 00 00 00
RSP: 0018:ffffc90000007a00 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88805dba6200 R08: ffff88805dba6200 R09: 00000000000000ff
R10: dffffc0000000000 R11: fffff52001831201 R12: ffff88805dba6288
R13: 0000000000000002 R14: 0000000000000000 R15: ffff88805dba6234
FS:  00007fa18785e6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a5b37ef950 CR3: 0000000036183000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
   0:	b6 0c                	mov    $0xc,%dh
   2:	19 84 c9 0f 85 b8 01 	sbb    %eax,0x1b8850f(%rcx,%rcx,8)
   9:	00 00                	add    %al,(%rax)
   b:	03 45 34             	add    0x34(%rbp),%eax
   e:	4c 8d a5 88 00 00 00 	lea    0x88(%rbp),%r12
  15:	4c 89 e1             	mov    %r12,%rcx
  18:	48 c1 e9 03          	shr    $0x3,%rcx
  1c:	0f b6 0c 19          	movzbl (%rcx,%rbx,1),%ecx
  20:	84 c9                	test   %cl,%cl
  22:	0f 85 c7 01 00 00    	jne    0x1ef
  28:	31 d2                	xor    %edx,%edx
* 2a:	41 f7 34 24          	divl   (%r12) <-- trapping instruction
  2e:	41 89 17             	mov    %edx,(%r15)
  31:	45 89 ec             	mov    %r13d,%r12d
  34:	eb 0f                	jmp    0x45
  36:	e8 0d a7 8a f9       	call   0xf98aa748
  3b:	48                   	rex.W
  3c:	bb                   	.byte 0xbb
  3d:	00 00                	add    %al,(%rax)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/05 08:13 linux-6.6.y 0a805b6ea8cd a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan divide error in comedi_inc_scan_progress
* Struck through repros no longer work on HEAD.